It is known that measuring the levels of urinary components is useful for health management. In particular, quantitative measurement of glucose concentration in urine is important as it provides a criterion to diagnose diabetes which is increasing year by year. A method for measuring glucose concentration in urine, i.e., urine sugar concentration, is known in the art which uses an enzyme-based biosensor in accordance with a glucose oxidase (GOP) method (refer, for example, to patent document 1).
In this method, when urine is brought into contact with an enzyme membrane formed by immobilizing GOP onto an electrode coated with a selective permeable membrane, the reactions shown by the following equations (1) and (2) take place, and the glucose concentration is obtained by measuring the amount of the electric current that flows.β−D−glucose+→D−glucono−δ−lactone+H2O2  (1)H2O2→2H++O2+2e−  (2)
A method is also known that measures the concentration of urine sugar by an optical method utilizing the optical activity of the urine sugar (refer, for example, to patent document 2). According to this method, since the measurement can be performed without directly contacting the urine, contaminants do not adhere to sensors, and the measuring system can be used for an extended period of time without requiring replacement of parts or consumables.
The method of measuring the concentration of an optically active substance in urine, utilizing the optical activity, is based on the following equation (3).θ= 1/100×[α]λT×c×L  (3)
θ is the angle of rotation due to optical activity, and generally, rotation to the right is taken as + and rotation to the left as −. [α]λT is the specific rotation of the optically active substance when the wavelength of light is λ and the temperature T, and is a constant unique to the substance causing the rotation. Further, c is the concentration of the optically active substance in the urine, and L is the optical path length of the sample (urine). In equation (3), since the specific rotation [α]λT, the wavelength λ, the temperature T, and the optical path length L are known, the concentration c can be obtained by measuring the angle of optical rotation θ.
However, urine contains many components other than the component to be measured. For example, in addition to the urine sugar (urine glucose) to be measured, urine contains interfering components such as vitamin C (ascorbic acid), peptides, amino acids, etc., excreted after taking nutritional supplements, etc. Vitamin C has a strong reducing power and affects the electric current used in the enzyme-based measurement; furthermore, since it is an optically active substance (specific rotation: 23°), it also affects the optical measurement utilizing the optical activity. Such interfering components not only contribute to degrading the accuracy of the measurement, but can contaminate the measuring parts.
In view of this, it is known to perform measurement after removing such interfering components (refer, for example, to patent document 3). For example, when measuring urine sugar, vitamin C and amino acids are removed using an ion-exchange resin, and peptides are removed using a synthetic adsorbent resin or activated carbon.
However, if a filtering mechanism containing such an ion-exchange resin, synthetic adsorbent resin, activated carbon, etc. is used continuously, part of the previously measured urine remains in the filtering mechanism itself, resulting in an inability to make an accurate measurement. One possible method to address this problem would be to clean the filtering mechanism with clean water or a cleaning liquid after use, but adding a cleaning mechanism would require installing a special cleaning container, leading to such problems as increasing the size and cost of the measuring apparatus while, at the same time, increasing the complexity of maintenance work.
However, the structure of a cassette for continuous measurement, including a specific flow channel design, has not been disclosed in the prior art. There has also been no disclosure of a specific cassette structure that addresses hygienic concerns, for example, by making provisions to prevent the hand from contacting liquids such as urine when removing the cassette.
It is known to clean the urine flow channel after measuring the urine, as described above, but in some cases, cleaning it with clean water may not be sufficient. In particular, to prevent growth of fungi, a special cleaning liquid may become necessary in addition to using clean water. In view of this, it is known to use ionized water generated by electrolyzing tap water (refer, for example, to patent document 4).
It is also known to provide an analyzing apparatus that uses analytical reagents instead of cleaning liquids (refer, for example, to patent document 5). This analyzing apparatus is designed to make optical measurements by using a single separation column (filled with resin) and a plurality of reagents for analyzing various kinds of amino acids.
However, storing large quantities of antiseptics, cleaning agents, or reagents in advance within the apparatus has involved problems in terms of space and maintenance. Furthermore, storing various kinds of cleaning liquids, etc. for various kinds of analytes in advance within the apparatus has also involved problems in terms of space and maintenance.    [Patent document 1] Japanese Unexamined Publication No. H11-271259 (FIG. 2)    [Patent document 2] Japanese Unexamined Publication No. 2000-81386 (FIG. 1)    [Patent document 3] International Publication WO 2005/093410 Pamphlet (FIG. 1)    [Patent document 4] Japanese Unexamined Publication No. 2002-98628 (FIG. 2)    [Patent document 5] Japanese Unexamined Publication No. H09-80037 (FIG. 3)